The present invention relates to a gas discharge display panel suitable for a large screen display in which the display brightness and light emission efficiency are improved and which has a high display accuracy. More specifically, the invention is intended to provide a gas discharge display panel suitable for a large screen display in which, with the size of each opening in cathode electrodes and the thickness of each cathode electrode suitably determined and/or the size of each discharge cell determined so as to be large compared with the size of the opening of the cathode electrodes, the distance between the front plate of the display panel and each cathode electrode is suitably determined in order to improve the display brightness and light emission efficienty. It is desired to accomplish this with no spacer employed thereby making the overall construction considerably simple.
An example of a conventional gas discharge display panel is shown in FIG. 1. In the gas discharge display panel 1, a number of ribbon-shaped or line-shaped anode electrodes 2 are arranged in parallel and a spacer 4 having a number of round holes 3 in which discharge takes place is disposed over the anode electrodes 2. A number of ribbon-shaped cathode electrodes 6 are arranged over the spacer 4 in such a manner that the cathode electrodes 6 are orthogonal with the anode electrodes 2. Small round holes 5 are cut in the cathode electrodes 6. The cathode electrodes 6 and anode electrodes 2 thus arranged are held through spacers 7 and 8 by a front plate 9 and a rear plate 10 which may, for instance, be glass plates. The front and rear plates 9 and 10 form the opposed outer walls of the display panel. The outer walls are sealed at peripheral portions thereof to form a vacuum container or envelope in which a gas containing primarily an inactive gas such as neon, argon, helium, xenon or crypton is sealed.
The conventional gas discharge display panel described above is disadvantageous in that if the capacity or the resolution power is increased, the display brightness and light emission efficiency are decreased.
As described above, the spacers 4, 7 and 8 are arranged in three layers in the conventional gas discharge display panel. These spacers suffer from problems in that, since their thickness is very small, typically about 200.mu., the spacers are liable to bend when used for a large area display, that is, it is difficult to maintain them flat, Moreoever, the spacers are difficult to produce making their cost high. Furthermore, the work needed to assemble the display panel using the spacers 4, 7 and 8 is intricate. Cutting a large number of small holes forming discharge cells in the spacers is costly. In addition, handling the components is troublesome in assembling the display panel. Thus, the conventional display panel is not suitable for a large screen display and it has a relatively low resolution power.
The conventional display panel will be described in more detail. FIG. 8a is a sectional view of the conventional display panel shown in FIG. 1. In FIG. 8A, reference numeral 11 designates a discharge cell, and 12 a space for forming a negative glow 13 between the front plate 9 and the cathode electrode 6. The thickness 5 of the spacer 7 is usually four to 25 times the mean distance between collisions (mean free path ) .lambda..sub.e of electrons and ions in a plasma created by the discharge.
In the operation of the conventional display panel, the negative glow 13 spreads downwardly from the edge of the opening 5 in the cathode electrode 6 as shown in the figure. More specifically, if the thickness S of the spacer 7 is set, for instance, to 6 .lambda..sub.e, the discharge display state of the display panel will be as shown in FIG. 8A. That is, the negative glow 13 spreads out downwardly from the central portion of the side wall of the opening 5. If the negative glow is viewed from above the front plate 9, it appears as shown in FIG. 8B. That is, the negative glow spreads only along the edge of the opening with no glow being effected in the center of the opening 5. If the thickness S of the spacer 7 is 20 .lambda..sub.e, the negative glow 13 spreads as shown in FIG. 8C. More specifically, in this case, although the negative glow does not spread over the upper surface of the cathode electrode 6, it spreads from the side wall of the opening 5 to the lower surface of the cathode electrode 6. If the negative glow is observed from above the front plate 9, the negative glow appears as shown in FIG. 8D. That is, the negative glow spreads substantially throughout the entire area of the opening 5 except for the center.
More generally, if the thickness of the spacer 7 is in the range of from 6 .lambda..sub.e to 20 .lambda..sub.e, the negative glow 13 does not spread over the upper surface of the cathode electrode 6 or towards the front plate 9. If it is attempted to cause the negative glow 13 to spread towards the front plate 9 by increasing the discharge current, it is difficult to form the negative glow 13 because of the charge particle loss to the front plate 9. Even if the negative glow were formed, it would be unstable. The discharge light emission of the negative glow 13 is limited as shown in FIGS. 8B and 8D, and accordingly the display brightness is low and the light emission efficiency is also low.
If the thickness of the spacer 7 is in the range of from 20 .lambda..sub.e to 25 .lambda..sub.e, because of variations in dimensions of the discharge cells during manufacture, the negative glow will spread over the upper surface of the cathode electrode 6 or towards the front plate 9 in some discharge cells but not in other discharge cells. Thus, in this case, the discharge display is not stable.